The aim for a more sustainable society demands high penetration of Renewable Energy Sources, RES, in all domains, including the residential sector. Furthermore, recent technology improvements made various renewable energy systems more available and easier to deploy, even in urban areas. Residential RES systems have been encouraged through guaranteed feed-in, leading to a high number of installed Photovoltaic panels in the residential sector. Furthermore, small-scale wind turbines that can be installed in urban zones have also become available in the market.
The high penetration of Distributed Energy Resources, DER, presents an issue for the stability of electricity grids which can be mitigated by local consumption of the generated energy. Also, local use of renewable energy should be favoured over feed-in since it results in higher efficiency. Moreover, the trends show that this will also be economically the most desirable option due to a decrease in feed-in rates—that are sometimes not available at all—and the emergence of grid-parity systems. The local consumption of energy is also motivated by the independence from the grid and devotion to green energy.
The main challenge with local consumption of renewable energies is how to match fluctuating supply and demand. Various approaches to balance between an intermittent energy source and power loads have been proposed. In the residential sector, a very common strategy is to shift in time the use of delay-tolerant appliances based on the availability of renewable energy.
The load balancing problem becomes more complicated once the demand comes from multiple users, requiring a certain form of fairness. Different notation of fairness for shared resources can be defined. For instance, with proportional-share fairness users are supposed to get the shared resource—here renewable energy—proportionally to their shares in the system. However, this type of fairness is not suitable for loads such as home appliances which operate only if they get the entire required amount of power equal to their power consumption. Another type of fairness can be defined as delay-fairness which considers the wait times experienced by users.
Usual practice with delay-tolerant loads is that a user submits a request together with a deadline until which the appliance should finish. These deadlines are hard deadlines meaning that the appliance must finish by the requested timestamp even if in that case additional grid energy has to be consumed. Contrary to renewable energy that is free after the initial investments, the additional grid energy comes at the price charged by the utility. Electricity pricing schemes may still differ from country to country but a general trend towards dynamic electricity pricing is obvious. With the electricity market deregulation and penetration of renewable energy at grid scale, a widely accepted view is that in future electricity price will depend on time of use, matching supply and demand. In this way residential customers would get a day-ahead “menu” with electricity prices changing every 15-30 min. Some variations of this pricing scheme are already in use.
Currently, users rarely actively share a renewable energy source in developed countries. For instance, in Germany there are still feed-in tariffs that are more profitable than local use of energy. However, this is going to change, Fulton et al., The German feed-in tariff: Recent policy changes. Furthermore, there are countries where neither this tariffs nor net-metering are available and the energy is consumed locally. For installation of renewable systems in residential building, not only a load balancing that minimizes additional costs is needed, what is provided by the current state of the art.
Contrary to developed countries, shared renewable systems used locally within a community are more frequent. Social studies show that a certain type of control over a use of particular users is desired, Jenny et al., Psychological factors determining individual compliance with rules for common pool resource management: The case of a Cuban community sharing a solar energy system. 